Gear wheel lapping tool



Aug. 29, 1933. T. R. RIDEOUT GEAR WHEEL LAPPING TOOL Filed April 2, 1931 INVENTOR Theodore EEG e002:

ATTORNEY Patented Augh29, 1933 UNITED S ATES 1,924,380 I GEAR WHEEL, LAPPING TOOL Theodore R. Rideout, Pittsburgh, Pa., assignor to Westinghouse .Electric& Manufacturing Company, a corporation of Pennsylvania Application April 2,1931. Serial No. 521,179 I a 5 Claims. (01 51-204) My ,invention relates, generally, to lapping tools and, more particularly, to lapping tools utilized for lapping the teeth. of large gear wheels.

5 In order to construct a gearwheel which will withstand the severe shocks and heavy loads to which it is subjected in service, it is necessary to harden it, after the teeth are cut, by subjecting it to a-heat-treating process. This process, invariably, causes the become distorted. In order to minimize the errors caused by these distortions, the teeth are lapped by a lapping tool, since the teeth aretoo hard to bere-suriaced by a cutting tool.

In general, the lapping process comprises applying an abrasive compound on the teeth of a gear wheel andthen reciprocating it in-and-out of a lapping tool. The lapping tool is disposed to encircle the gear wheel and is provided with inwardly projecting complementary teeth which mesh with the teeth of the gear Wheel. In order to providefor lapping all thejteethevenly, the gear wheel is disposed to be turnedwithin the lapping tool by indexing the teeth, one at a time, at the beginning of each reciprocatory movement.

Although the process of "lapping 'gear teeth has been "appliedto small gear wheels,; it has applied to large gear wheels, because never been of the difficulty encountered in" constructing large lappingtools. In constructing a lapping tool for small gear wheels, a solid lapping 'meinberis cast around the teeth of a dummy gear wheel, which is essentially like the gear wheel 3 to be lapped. However, in order that a. substantially long. lapping stroke and the proper, clearance between the lapping tool and the gear wheel to be lapped, may be provided, the dummy gear wheel is provided with a wider face and a slightly larger diameter than .the corresponding dimensions of the gear wheel to' belapped."

In endeavoring to construct a-1apping".tool

for large gear wheels, many attempts were made,

to cast a solid lapping'member arounda large dummy gear wheel in the samelmanner astfor small gear wheels, but such attempts were unsuccessful because internal stresses were .set-up during the cooling of the metal. ..The'internal o stresses were so great that either I ping member broke or the dummy gear'wheel was crushed. In order to overcome this-difficulty, the dummy gear wheel was heatedin order to provide a similar shrinkage to thatof the solid lapping member, but thismethod' was also teeth of the gear wheel to become apparent.

the lobjects ofthe invention, reference should be the sen lap wheel andtheannulusthus forming a plurality unsuccessful because of' the fusion of the two members. I

. Also, several attempts were made to cast individual lapping members, which covered only a small section of, .the teeth of the dummy gear v lapping, members are restrained from.warping during'the cooling'process.

,Another object of my invention is to provide for forming individual lapping members for a r 5 lapping tool by pouring molten metal intothe 7 space providedintermediatea dummy gear wheel and an annulus which is, disposedgto encircle the dummy gear wheel. i

A further object of my invention isto provide for mounting individual lapping members ona support whereby adjustments may-be made to compensate for the wearingyof the lapping members, caused by the lapping process;

I Other objects of the invention will hereinafter 5 This invention, accordingly, is-disclosed in the accompanying drawing and comprises the features of construction, the combination ofelements and the arrangement of .parts which will be exemplified in the construction hereinafter set forth and the scope of th e application of which will be indicated in the claims.

' For a fuller understanding of the nature and e had to the following detailed descriptiomtaken in connection with the accompanying drawing, in

which. 1

Figure 1 is aplan view illustratingthe erg rangement of the partsutilizedin constructing 160 a lapping tool embodying the features of my. invention, comprising a dummy gear wheel cen-f. trally disposed within an annulus having cores equally spaced. K a

Fig. 2 is a plan view" with parts in section il lustrating the same elements that arelshown in Figijl, withthe additionof a body of metalin the spaces provided between the dummy) gear the cores. al, the annulus restrains the lapping members Fig. 3 is a plan view of a lapping tool constructed in accordance with my invention, parts being broken away to show the bolts that are utilized to connect the individual lapping members to the annulus;

Fig 4 is a sectional view of a lapping tool taken along the line IV-JVof Fig. 3, and a gear wheel which is disposed to be lapped.

Fig. 5 is a'fragmentary sectional view of my lapping tool, illustrating, particularly, the shims,

whereby the lapping members may be adjusted in order to compensate for wear,

Referring now to the drawing; 12 designates, generally, an annulus which is utilized to construct my lapping tool. As shown, it is. disposed to encircle a dummy gear wheel 10, preparatory to the pouring of the molten metal for forming the individual lapping members 18. The annulus is constructed to have a face of substantially the same width as the face of the dummy gear wheel. Also, itis of such size as to be strong enough to restrain the lapping members from warping away from the dummy gear wheel.

In order to form a plurality of individual lapping members, a plurality of cores 14 are provided at evenly spaced intervals, between the dummy gear wheel and annulus. Any number of cores may be utilized, the number depending somewhat upon the size of the gear wheel to be lapped.

When molten metal is poured, for forming the lapping member, it completely fills thespace intermediate the dummy gear wheel and the an-- nulus, except that space which is stopped off by Upon the cooling of the molten metfrom'warping away from the teeth of the dummy gear as they would have done had the annulus not been utilized.

However, in order to keep the magnitude of the internal stresses which are set-up during the cooling. process, from becoming excessive, the width of the space between the dummy gear wheel 10' and the annulus 12 is made as small as possible. It will be observed that, by pouring a' plurality of individual lapping members instead of one continuous member between the dummy gear wheel and the annulus, the stresses are smaller, because each'member is free to contract linearly.

After cooling, and before the dummy gear is removed, the annulus 12 and'the individual lapping members 18 are drilledand tappedin order that they maybe secured together by bolts 20.

It has been determined that, if the webbed recess 11' of the'dummy gear wheel 10 is filled with cool water, and the annulus 12 is heated, the dummy gear wheel may be readily removed.

In order to provide for adjusting the lapping members relative to the annulus whereby means may be provided to compensate ior wear, shims 26 are utilized. As shown in Fig. 5, the shims 26 are inserted intermediate the, individual lapping members 18 and the annulus 12.

In view of 'the'fact that'means of anysuitable type may be utilized to reciprocate the gear wheel in-and-out of the lapping tool, only a showing of the essential parts is included in the drawing, such as, for example, in Fig. 4, a gear wheel 24 is disposed on a shaft 25 which may be reciprocatedby a suitably operated piss ton.

At first, since theteeth of the lapping. members may be imperfect, the lapping process laps not only the errors that may be present in the teeth of the gear wheel, but also the errors that may be present in the teethof the individual lapping members. However, it will be observed that the teeth of the lapping members become more nearly perfect the more the lapping tool is utilized, and eventually, substantially all the lapping will occur. on the teeth of the'gear wheel instead of on both. 1

While the illustrated example constitutes a practical embodiment of my invention, I do not limit myself strictly. to the exact details here illustrated, since the structure and the method of making it may be considerably varied without departingi'rom the spirit of the invention, as defined in the appended claims.

I claim as my invention:

1'. A lapping tool utilized for lapping the teeth of gear wheels comprising, in combination, a plurality of segmental lapping members, an annulus for supporting said lapping" members, means for detachably securing the lapping members in spaced relation to the annulus, the lapping members having teeth thereon, the con-' tour of said teeth constituting a lapping surface for so lapping the teeth of gear wheels that the contour and the positionof each tooth of the gear wheel, when lapped, relative to each successive tooth thereof, are the same.

2. A lapping tool utilized for lapping the teeth of-gear wheels comprising, in combination, an annulus, a sectioned lapping member disposed within said annulus and having teeth formed thereon, the contouroi said teeth constituting a lapping surface for so lapping the teeth of gear wheels that the contour and the position of each tooth cf the gear wheel, when lapped, relative to each successive tooth thereof, are the same. means for detachably connecting. the lapping member to the annulus, and means for adjusting the segmental lapping member relative to the annulus in order to compensate for the wear caused by the lapping process.

3. A lapping'tool utilized for lappingthe teeth of gear wheels comprising, in fcombinatioma plurality of segmental arcuate lapping, members having teeth formed thereon, means for supporting said lapping members, the contour of I tooththereof, are the same, meansv for detachably: connecting the lapping members to' the said supporting means, and means for adjusting the segmental lapping'me'mbers relative to the; supporting means'in order to compensate for the wear caused by the lapping process.

4. The method of constructing a'lapping tool utilized for lapping the teeth of gear wheels comprising constructing an annulus having a greater internal diameter than :the externaldiameter of 'thefgear wheel to belapped, constructing a dummy gear wheel having the same teeth contour as'that of'the teeth" of the gear wheel to-belapped, positioning the dummy gear wheel within the annulus, positioning a plurality'of corezimembers between the dummy gear wheel and theiannulua; pouring moltenmetal into the remaining space intermediate the dummy gear wheel and theannulus, thus forming. a plurality of segmental arcuate lapping membersmhaving lapping surfaces adjacent, to the teeth, of the dummy gear wheel; and removing the dummy gear wheel from the annulus.

5.- The method of constructing a lapping tool utilized for lapping the teeth of gear wheels comprising constructing a supporting member having an opening larger than the gear wheel to be lapped, constructing a dummy gear wheel having the same teeth contour as that of the teeth of the gear wheel to be lapped, positioning the dummy gear wheel within the opening of the supporting member, positioning a core member between the dummy gear wheel and the sup- ,THEODORE R. RIDEOUT. I 

